Federal Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income taxes paid or refunded, net	$ 0	$ 23,600
Income tax examination description	American National’s federal income tax returns for years 2016 to 2018 are subject to examination by the Internal Revenue Service.

The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4297-108586

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration